The present invention relates generally to digital imaging systems and, more particularly, to a system and setup procedure for determining a variable setpoint for laterally centering a radiation source with respect to a digital detector in a digital imaging system.
The installation and setup procedure for digital imaging systems, such as digital radiographic imaging systems, can be complex and time-consuming. To comply with customer image quality and consistency requirements and various regulatory and safety standards, the procedure generally requires the determination of a variety of constants including the positioning of the x-ray source with respect to the detector. For example, the determination and establishment of fixed setpoints for laterally centering the x-ray source with respect to the center of the detector often is a required procedure. Among the problems associated with the failure to accurately determine lateral center-to-center setpoints in radiographic imaging system are image decentering and cutoff
Generally, known installation and setup procedures for determining lateral center-to-center setpoints require that a field engineer geometrically determine the lateral centerline of the detector and then generate and detect several x-ray fields with the x-ray source located at a variety of positions laterally displaced from one another. Eventually, through trial and error, the field engineer can determine a laterally centered source position at which the x-ray field generated by the source is laterally centered with respect to the lateral centerline of the detector when the detector is fixed at a particular position. Once the laterally centered source position is found, the field engineer sets a fixed detent setpoint to mark the location. For example, the field engineer may install an electromechanical switch or other device in the ceiling or the superstructure of the x-ray source that will tactilely, and perhaps audibly, indicate to users of the imaging system that the x-ray source is at a laterally centered position.
This iterative setup procedure becomes even more complex when the detector is movable between locations. In such event, the field engineer must repeat the setup procedure at multiple locations of the detector and install several setpoint or detent devices at the corresponding multiple laterally centered source positions. Still further, many examination rooms may include more than one detector that can be used with the same x-ray source. For example, an examination room may include a horizontal patient table with a first detector that is movable along the longitudinal axis of the table, as well as an upright positioner with a second detector that is movable along the vertical axis of the positioner. Such a setup requires the determination of laterally centered source positions with respect to multiple detector positions for each detector.
Once a laterally centered source position is determined and marked with a setpoint device (e.g., a tactile switch), the position is fixed. Thus, a user of the imaging system is not afforded flexibility in the event that the user might desire to position the detector in a position other than the positions for which laterally centered setpoints were determined. Accordingly, even though a detector could be continuously movable along a track such that patients of various sizes could be accommodated or various anatomical parts could be more easily imaged, the positions in which the detector could accurately be used would be restricted to only those few detector positions which had corresponding fixed source setpoints. Otherwise, image decentering or cutoff may occur.
Fixed setpoints can also result in decreased system reliability because the physical switches or detent devices increase the number of components which can potentially fail during system usage.
Thus, it would be desirable to provide a system and method for setting up a digital radiographic imaging system that would avoid time-consuming iterative procedures for determining source positions setpoints that are laterally centered with respect to the lateral centerline of the detector. It would be further desirable if such a setup system and method would result in the elimination of fixed setpoints and physical fixed setpoint devices, thus affording greater flexibility and increasing the reliability of the system.
The present invention addresses one or more of the shortcomings noted above.
For example, a method for determining a lateral center-to-center setpoint for a digital imaging system having a digital detector and a radiation source includes positioning a detector having a lateral centerline at a first detector position, positioning the radiation source at a first source position, generating a first radiation field that is detectable by the detector, detecting the first radiation field at the detector, and determining a first lateral centerline of the first radiation field. The radiation source is then positioned at a second source position that is displaced from the first source position at least in a lateral direction, followed by generating a second radiation field that is detectable by the detector, detecting the second radiation field at the detector, and determining a second lateral centerline of the second radiation field. A lateral gain constant may then be determined based on the determined first and second lateral centerlines and the first and second source positions.
In another aspect of the present technique, a method for determining a lateral center-to-center setpoint of a digital imaging system having a radiation source that generates a radiation field detectable by a digital detector is provided. The method includes determining a first lateral centerline of a first detected radiation field generated when the radiation source is at a first source position, determining a second lateral centerline of a second detected radiation field generated when the radiation source is at a second source position laterally displaced from the first source position, and determining a system gain constant based on the determined first and second lateral centerlines and the first and second source positions. The system gain constant may then be utilized to automatically determine a laterally centered source position at which a radiation field generated by the source is substantially laterally centered with respect to a lateral centerline of the detector.
In another aspect of the technique, a system is provided for automatically determining a lateral center-to-center setpoint of a radiation source with respect to a digital detector. The system includes a radiation source to generate a radiation field, the radiation source being movable at least along a source lateral axis and configured to generate a first radiation field at a first source position and a second radiation field at a second source position laterally displaced from the first source position. The system further includes a digital detector having a lateral centerline, the digital detector being configured to detect the first and second radiation fields and to generate detector signals representative thereof. The system also includes a processing module that is configured to determine a first lateral centerline of the first radiation field based on the detector signals representative of the first radiation field, determine a second lateral centerline of the second radiation field based on the detector signals representative of the second radiation field, and determine a lateral gain constant based on the first and second lateral centerlines and the first and second source positions.